Today spectral detection devices, such as spectrometers, are increasingly used in light management applications, for example, to measure the color point and color rendering index of light to determine the atmosphere created by a number of luminaries, and/or to monitor light emitted by a specific luminary.
A typical example of a light management application using a spectrometer is an ambient intelligent lighting system that allows a user to flexibly determine the atmosphere created by a number of luminaries in a room. To achieve the desired atmosphere the ambient intelligent system measures and controls the lighting characteristics of each individual luminary by a control feedback system that measures the intensity, color point and color rendering index of the individual luminaries.
Furthermore, a spectrometer may also be used to monitor light color in modern luminaries, in which white light is generated by light emitting diodes (LEDs), for example with a red, green and blue (RGB) LED (or more and/or different colors of LEDs). Here, monitoring of the light color is important since the mixed light from the LEDs only results in white light if the light from each individual LED is properly combined with the light coming from the other LEDs.
WO2008/012715 discloses an integrated image recognition and spectral detection device comprising an image sensor array for recognizing images and motion, and a Fabry-Perot resonator structure for detecting spectral components of received light which covers at least a part of the light-sensitive surface of the image sensor array. To be able to measure multiple spectral components of the received light, the Fabry-Perot resonator structure is segmented into a chessboard-like structure, where each segment has a different thickness to provide a different spectral component. Further, the arrangement is such that each spectral component is detected by a different sensor in the image sensor array. In operation, the image sensor array continuously detects the spectral components contained in the incident light and transmits corresponding signals to a control means. The control may then adjust the electric current for the LEDs separately based on the detected spectral components and a color setting control algorithm, in order to achieve a desired color point.
However, even though the spectral detection device disclosed in WO2008/012715 may satisfactorily measure the spectral components of received light, it is costly to deposit an array of multilayered interference filters close together. Therefore it may be desirable to provide a low cost alternative spectral detection device that does not require many (expensive) deposition and lithography steps. There is also a desire to have a more compact device compared to the prior art. In WO2008/012715 many filters are used with narrow spectral bands in order to measure spectral components. To achieve a device that is sensitive enough to detect light levels on the order of 100 lux, the pixel areas cannot be reduced to a very small area, limiting the size reduction options for the device. Thus, there seem to be a need for an alternative spectral detection device.